I sent Nordea an e-mail on December 5 after we had spoken to them on the phone about the Swish number not being the one we wanted. I haven't received a reply yet, so I called them today, December 10.
They were not able to give me any information about our accounts or orders, because I'm not an authorised representative. They said they would be able to fix the Swish number issue, but only if an authorised representative calls them. (They also wouldn't give me any information about whether the application for bankgiro had reached them despite having answered this question last week, they were probably getting suspicious of me because I asked so many questions about the accounts. So I'm not sure whether the application for bankgiro has reached them or not.)
@Jopparn will you have time to call Nordea some time during the week?
Resolved issue, included for information
The one I spoke to at Nordea on December 10 couldn't find any information about it being possible to have a Swish number that is the same as the 90-account number, and asked me to contact Swish about this. Swish don't have a support phone number, so I sent them an e-mail. They answered and said that we should try and contact Nordea again, because it is possible and it is set up via the bank.